Chem-test 3

1) Which of the following statements about Lewis structures is FALSE? A) An octet is when an atom has 8 valence electrons. B) A duet is a stable electron configuration for helium. C) An ionic bond occurs when electrons are transferred. D) A covalent bond occurs when electrons are shared. E) All of the above statements are true.

2) Which Lewis structure below correctly represents the compound formed between magnesium and sulfur? A) Mg+ [: :]- B) Mg+ [: :]2- Mg+ C) [: :]- Mg2+ [: :]- D) Mg2+ [: :]2- E) none of the above

3) Lewis theory predicts that the formula for a compound between potassium and sulfur is: A) KS B) K2S C) KS2 D) K3S E) none of the above Answer: B

4) Lewis theory predicts that the formula of a compound formed between bromine and aluminum is: A) AlBr B) Al2Br C) AlBr3 D) AlBr2 E) none of the above Answer: C

5) When a nonmetal bonds with a nonmetal A) a molecular compound forms. B) a covalent bond is involved. C) electrons are shared. D) all of the above are true E) none of the above Answer: D

6) What is the correct Lewis structure for O2? A) O-O B) : - : C) = D) : O ≡ O : E) none of the above Answer: C

7) What is the correct Lewis structure for water? A) H-: :-H B) : - - : C) H= =H D) H- -H E) none of the above Answer: D

8) The central atom in the chlorate anion, ClO3- is surrounded by A) two bonding and two unshared pairs of electrons. B) one bonding and three unshared pairs of electrons. C) three bonding and one unshared pair of electrons. D) two double bonds and no unshared pairs of electrons. E) none of the above. Answer: C

9) The Lewis structure for carbon monoxide is This structures shows A) 4 lone pairs and 1 bonding pair. B) 4 lone pairs and 3 bonding pairs. C) 2 lone pairs and 3 bonding pairs. D) 2 lone pairs and 1 bonding pair. E) none of the above Answer: C

10) What is the correct Lewis structure for CN−? A) [C-N] − B) [: - :]− C) [ = :]− D) [: C≡ N :] − E) none of the above Answer: D

11) Which sequence below represents the proper order of increasing bond strength? A) single < double < triple B) double < single < triple C) single < triple < double D) triple < double < single E) none of the above Answer: A

12) Which symbol should be used between two structures that represent resonance structures? A) → B) ← C) ↔ D) ≡ E) none of the above Answer: C

13) How many valence electrons are in the nitrate ion? A) 18 B) 22 C) 23 D) 24 E) 26 Answer: D

14) Consider the Lewis structures for the compound SO3 and the polyatomic ions SO32- and SO42-. Which of these would exist as a set of resonance structures? A) SO3 only B) SO32- only C) SO42- only D) all of these show resonance E) none of these show resonance Answer: A

15) The central atom in the chlorate anion, ClO3- is surrounded by A) two bonding and two unshared pairs of electrons. B) one bonding and three unshared pairs of electrons. C) three bonding and one unshared pair of electrons. D) two double bonds and no unshared pairs of electrons. E) none of the above. Answer: C

18) What is the electron geometry if you have 3 electron groups around the center atom? A) linear B) trigonal planar C) tetrahedral D) trigonal bipyramidal E) not enough information Answer: B

17) What is the correct Lewis structure for CO2? A) : - - : B) : = = : C) : = C= : D) : = C= : E) none of the above Answer: D

19) The correct Lewis structure for BF3 would have exactly: A) 1 double bond. B) 2 double bonds. C) 1 triple bond. D) no double bonds. E) none of the above Answer: D

20) Which of the following compounds would have a linear molecular geometry? 1. N2 2. H2S 3. CO2 A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) 1,2 and 3 E) neither 1, 2,or 3 Answer: B

21) Which set shows the correct resonance structures for SeO2? A) : - - : ↔ = = B) : = - : ↔ : - = : C) : =Se= ↔ : O≡ Se- :↔ : -Se≡ O : D) = - : ↔ : - = E) SeO2 does not have a resonance structure. Answer:

22) What is the angle between electron groups in the trigonal planar electron geometry? A) 90° B) 109.5° C) 120° D) 180° E) not enough information Answer: C

23) The electron geometry and the molecular geometry of ammonia (NH3) are, respectively, A) trigonal planar, bent. B) tetrahedral, tetrahedral. C) tetrahedral, trigonal pyramidal. D) tetrahedral, bent. E) none of the above Answer: C

24) Which compound listed below will dissolve in water? A) CCl4 B) SiO2 C) NH3 D) all of the compounds E) none of the compounds Answer: C

25) How does soap work? A) Soap works by breaking grease molecules into smaller molecules that dissolve in water. B) Soap works by making water into a nonpolar liquid which grease can dissolve in. C) Soap works by having a polar end and a nonpolar end which allows the water and oil to interact indirectly. D) Soap works by by having a polar end which attaches to the grease molecule and polarizes it and turns the grease molecule into another soap molecule. This is a chain reaction. E) none of the above Answer: C

26) The electronegativity value for Mg is 1.2 and the value for O is 3.5. Based on these values, what type of bond is expected for a compound formed between Mg and O? A) Ionic B) Pure covalent C) Polar covalent D) not enough information E) none of the above Answer: A

27) Which of the following statements about the water molecule is TRUE? A) A water molecule has two dipole moments and they cancel each other. B) A water molecule is symmetrical and therefore is nonpolar. C) A water molecule is asymmetric and therefore is polar. D) The electronegativities of hydrogen and oxygen are equal and therefore a water molecule is nonpolar. E) none of the above Answer: C

28) Which molecule listed below is a nonpolar molecule? A) CCl4 B) CO2 C) BH3 D) all of the compounds E) none of the compounds Answer: D

29) Which term matches the definition: The ability of an element to attract electrons within a covalent bond? A) coulombic attraction B) dipole moment C) polar covalent D) nonpolar covalent E) electronegativity Answer: E

30) The elements with the highest electronegativity values tend to be found in the: A) upper right-side of the periodic table. B) lower right-side of the periodic table. C) upper left-side of the periodic table. D) lower left-side of the periodic table. E) center of the periodic table. Answer: A

1) What is the volume of 28.0 g of nitrogen gas at STP? A) 33.6 L B) 11.2 L C) 22.4 L D) 44.8 L E) none of the above Answer: C

2) If the number of moles of a gas initially contained in a 2.10 L vessel is doubled, what is the final volume of the gas in liters? (Assume the pressure and temperature remain constant.) A) 6.30 B) 1.05 C) 4.20 D) 8.40 E) none of the above Answer: C

3) What is the final volume of a gas that initially occupies 2.50 L at 298 K and is subsequently heated to 321 K? A) 2.69 L B) 2.96 L C) 2.23 L D) 2.32 L E) none of the above Answer: A

4) How many liters of O2 (g) are needed to react completely with 56.0 L of CH4 (g) at STP to produce CO2 (g) and H2O (g)? Given: CH4 (g) + 2O2 (g) → CO2 (g) + H2O (g) A) 28.0 L B) 56.0 L C) 84.0 L D) 112. L E) none of the above Answer: D

5) Which set of conditions reflect STP? A) 298 K, 1 atm B) 25°C, 14.7 psi C) 373 K, 760 torr D) 273 K, 1 Pa E) 273 K, 760 mm Hg Answer: E

6) A balloon filled with 0.500 L of air at sea level is submerged in the water to a depth that produces a pressure of 3.25 atm. What is the volume of the balloon at this depth? A) 1.63 L B) 0.154 L C) 6.50 L D) 0.615 L E) none of the above Answer: B

7) Hydrogen gas produced in the laboratory by the reaction of zinc and hydrochloric acid was collected over water at 25°C. The barometric pressure at the time was 742.5 mm Hg. What is the pressure of dry hydrogen gas if the vapor pressure of water at 25°C is 23.8 mm Hg? A) 742.5 mm Hg B) 718.7 mm Hg C) 766.3 mm Hg D) 760.0 mm Hg E) none of the above Answer: B

8) The vapor pressure of water at 20.0°C is 17.5 mm Hg. If the pressure of a gas collected over water was measured to be 453.0 mm Hg. What is the pressure of the pure gas? A) 0.0230 atm B) 0.619 atm C) 0.573 atm D) 0.596 atm E) none of the above Answer: C

9) A gas cylinder contains only the gases radon, nitrogen, and helium. The radon has a pressure of 222 torr while the nitrogen has a pressure of 446 torr. If the total pressure inside the cylinder is 771 torr, what is the pressure that is due to the helium? A) 771 torr B) 668 torr C) 549 torr D) 103 torr E) none of the above Answer: D

10) Which of the following diatomic elements would have a mass of 19.08 grams stored in a 3.82 L container at 3,632 mm Hg and 100°C? A) H2 B) Br2 C) F2 D) O2 E) not enough information. Answer: D

11) A 3.76 g sample of a noble gas is stored in a 2.00 L vessel at 874 torr and 25°C. What is the noble gas? (R= 0.0821 L atm/ mol K) A) He B) Ne C) Ar D) Kr E) not enough information Answer: C

12) To solve problems using Charles's Law, which mathematical equation should be used? A) = B) T1V1 = T2V2 C) = D) P2V1 = P1V2 E) none of the above Answer:

13) A sample of 0.255 mole of gas has a volume of 748 mL at 28°C. Calculate the pressure of this gas. (R= 0.0821 L ∙ atm / mol ∙ K) A) 8.42 atm B) 0.784 atm C) 0.00842 atm D) 7.84 × 10-4 atm E) none of the above Answer: A

14) The ideal gas law is: A) PV = nRT B) P = C) T = D) V = E) All of the above are forms of the ideal gas Answer: E

15) Avogadro's Law is expressed as: A) V is proportional to B) P is proportional to n C) n is proportional to D) V is proportional to n E) none of the above Answer: D

16) Gas density can be calculated by dividing the mass of gas by its volume. If you took a balloon of gas and then warmed the balloon in a sunny window, what can now be said about the density of the gas in the balloon? A) The gas density will remain the same. B) The gas density will increase. C) The gas density will decrease. D) The density of gases is independent of temperature. E) none of the above Answer: C

17) Which one of the following is impossible for an ideal gas? A) = ( ) B) = C) V2 = ( ) V1 D) V1T1 = V2T2 E) none of the above Answer: D

18) Which of following statements are consistent with the Kinetic Molecular Theory? A) Gases are compressible because the volume of atoms is almost entirely open space. B) Gases assume the shape and volume of their container because they are in constant, straight-line motion. C) Gases have a low density because there is so much empty space between the particles. D) Gas particles collide with each other and surfaces without losing any energy. E) All of the above statements are consistent with the Kinetic Molecular Theory. Answer: E

19) . What is the pressure of a 1.0 L flask containing 0.60 g of He at 25°C? (R= 0.0821 L atm/ mol K) A) 98 atm B) 3.7 atm C) 7.3 atm D) 15 atm E) none of the above Answer: B

20) What is the final pressure (atm) of a 3.05 L system initially at 724 mm Hg and 298 K that is compressed to a final volume of 2.51 L at 273 K? A) 1.06 B) 1.60 C) 806 D) 860 E) none of the above Answer: A

21) Water can be formed according to the equation: 2H2 (g) + O2 (g) → 2H2O (g) If 8.0 L of hydrogen is reacted at STP, exactly how many liters of oxygen at STP would be needed to allow complete reaction? A) 4.0 L B) 2.0 L C) 1.0 L D) 8.0 L E) none of the above Answer: A

22) Suppose you had a balloon containing 1 mole of helium at STP and a balloon containing 1 mole of oxygen at STP. Which statement is TRUE? A) The balloons will have the same volume. B) The balloons will have the same mass. C) Both A) and B) are true. D) Neither A) nor B) are true. E) not enough information

23) Human lungs have evolved to breathe oxygen at a pressure as that in the atmosphere, 0.21 atm. If a particular heliox mixture to be carried by a scuba diver is at a pressure of 7.00 atm, what should be the partial pressure due to helium in order to maintain the pressure due to oxygen at 0.21 atm? A) 0.21 atm B) 7.00 atm C) 6.79 atm D) 7.21 atm E) none of the above Answer: C

24) A "shielding gas" mixture of argon and carbon dioxide is sometimes used in welding to improve the strength of the weld. If a gas cylinder of this two-part mixture was at 4.0 atm pressure and this mixture was 90.% argon, what would be the pressure due to the carbon dioxide gas component? A) 3.6 atm B) 0.40 atm C) 10. atm D) 4.0 atm E) none of the above Answer: B

25) Which conditions can cause nonideal gas behavior by 1) decreasing the space between gas particles or 2) by slowing gas particles so that interactions are significant? A) 1) high pressure; 2) high temperature B) 1) high pressure; 2) low temperature C) 1) low pressure; 2) high temperature D) 1) low pressure ; 2) low temperature E) none of the above Answer: B

26) For an ideal gas, which of the following pairs of variables are inversely proportional to each other (if all other factors remain constant)? A) P, V B) P, T C) V, T D) n, P E) none of the above Answer: A

27) What is the initial temperature (°C) of a system that has the pressure decreased by 10 times while the volume increased by 5 times with a final temperature of 150 K? A) 27 B) 75 C) -198 D) 300 E) none of the above Answer: A

28) Gas density can be calculated by dividing the mass of gas by its volume. If you took a balloon of gas and then warmed the balloon in a sunny window, what can now be said about the density of the gas in the balloon? A) The gas density will remain the same. B) The gas density will increase. C) The gas density will decrease. D) The density of gases is independent of temperature. E) none of the above Answer: C

29) Which set of conditions reflect STP? A) 298 K, 1 atm B) 25°C, 14.7 psi C) 373 K, 760 torr D) 273 K, 1 Pa E) 273 K, 760 mm Hg Answer: E

30) Suppose you had a balloon containing 1 mole of helium at STP and a balloon containing 1 mole of oxygen at STP. Which statement is TRUE? A) The balloons will have the same volume. B) The balloons will have the same mass. C) Both A) and B) are true. D) Neither A) nor B) are true. E) not enough information Answer: A